DESCRIPTION: (Adapted from applicant?s abstract): A critical but under-represented area of research in cognitive psychology and cognitive neuroscience concerns mechanisms responsible for adaptive regulation of cognitive control. One recent computational model that addresses this neglected subject holds that the mesencephalic dopamine system conveys reinforcement learning signals to motor areas in anterior cingulate cortex, where they are used to improve performance on the task at hand. According to the model, the transfer of negative reinforcement learning signals to anterior cingulate cortex elicits the "Error-related Negativity," an event- related brain potential (ERP) observed when human subjects commit errors in psychological reaction-time tasks. The goal now is to explore and extend this account by testing it against a competing theory of the ERN, by testing several additional predictions of the model, and by integrating it with an existing model of the mesencephalic dopamine system. The proposed studies consist of two combined functional magnetic resonance imaging/ERP experiments, two additional ERP experiments, and a computational modeling project. This research is expected to elucidate the nature of several clinical disorders associated with impairments of executive control, including schizophrenia, Huntington?s disease, obsessive-compulsive disorder, and frontal damage.